21 July 2009

Nem Hunt Day 2: Pulau Sekudu

Another 2am start and today we explore Pulau Sekudu! Also called Frog island, it lies just off Chek Jawa on Pulau Ubin, and is one of the best marine sites among our Northern shores.And what wondrous 'nems we saw today!

The small neat maroon anemones in the photo above are often clustered together like a bunch of flowers, so I've given it a lame name of Posy anemone (please help if you can think of a better common name). So far, I've only seen them in abundance on Pulau Sekudu. The last time Dr Daphne was on Pulau Sekudu in Jul 07, we didn't see many of them! So it was a great relief to find lots of them today.

I also managed to show Dr Daphne these strange green and red anemones that so far, I've only seen on Pulau Sekudu.Similar in shape to the Posy anemones, but much much larger. They are also found in deeper water. Are they something different? It's great to have Dr Daphne to look into this.

We also found another strange anemone. I forgot to take a photo of it in the excitement, but it looks like this one that I saw at Changi in Jun 08 (photo below). James also saw something similar at Cyrene in Jun 09.Here's a closer look at it. Another mystery for Dr Daphne to look into!We saw lots of the usual common anemones like the Haddon's carpet anemone (Stichodactyla haddoni). Dr Daphne shared that the sea anemone was named after a famous biologist and anthropologist, Alfred Cort Haddon. We sure learn a lot walking with Dr Daphne.I saw one Haddon's carpet anemone with a strangely distended area near the mouth (photo on the right). Did it just eat something large? We also saw the tiny Stichodactyla tapetum but I didn't manage to take a photo of it. Dr Daphne explains that the S. tapetum looks like a miniature S. haddoni. That is, the tentacles are proportional to the size of the oral disk. And of course, S. tapetum doesn't have the pattern of long-short tentacles on the edge of the oral disk.

This ball of tentacles is the Swimming anemone (Boloceroides mcmurrichii). And Dr Daphne showed one actually swimming! They come in a variety of patterns and shades of brown and yellow. Dr Daphne's student, Andrea, is studying these interesting animals. Today we were very fortunate to have Grace join us despite her having a long working day earlier. Dr Daphne shared with Grace lots of wonderful stories about science, scientists and of course, anemones. Stories about deep sea anemones and more. We hovered around to listen and learn as well.I only noticed today that Dr Daphne has a neat clip-on LED light thingy on her cap to see with at night! Wow, that's quite cool.

Our focus was on anemones, and we did spend a lot of time and effort to take a closer look at them. But Pulau Sekudu is teeming with so much life that we can't help but see other marine life as well. Here's some of the animals we saw purely by chance.

Today, there were a lot of little Flowery sea pens (Family Veretillidae, Order Pennatulacea) dotting the seagrass meadows. They come in a wide range of colours.As well as many Peacock anemones (Order Ceriantharia) - no photos though, today. Although they may resemble sea anemones, especially in the ripply waters, these two kinds of animals are not true sea anemones (Order Actiniaria).

Another nemish animal is the white spiral fan worm (Family Sabellidae) that were abundant today. The Vegas dancing girls of worms, these are segmented worms live in tubes with a feathery fan on their heads. When alarmed, these nervous worms disappear instantly into their tubes.Marcus came across a Banded file snake (Acrochordus granulatus)! The snake eats mainly small fishes. It has a loose skin covered with small rough scales which helps it to grip its slippery prey. The snake is harmless to humans and has tiny eyes and a small mouth.Pulau Sekudu is particularly rich in sea stars. Today, besides the many Biscuit sea stars (Goniodiscaster scaber) that are often seen here, I also saw these different sea stars in my short route through the little island.Clockwise from left: The Eight-armed sand star (Luidia maculata), several Painted sand stars (Astropecten sp.), some Plain sand stars (Astropecten sp.), an odd speckled Crown sea star (Astropecten coronata), several Cake sea stars (Anthenea aspera) and a Spiny sea star (Gymnanthenea laevis).

It was a special treat to see three large Knobbly sea stars (Protoreaster nodosus) within a small area of seagrass and coral rubble. They were large: about 30cm in diameter from arm tip to tip.There were also plenty of white sea urchins (Salmacis sp.), and a few thorny sea urchins (Prionocidaris sp.).And this rather handsome sea cucumber that looks very much like a Garlic bread sea cucumber (Holothuria scabra). Except that its body pattern is particularly rich and more colourful than the ones I usually see.Pulau Sekudu is also a great place to spot nudibranchs! Even short-sighted me found some. Like this Armina nudibranch (Armina semperi). I haven't seen one of these for a long long time! In the armina nudibranchs, the gills are hidden beneath the body mantle above the foot, so it doesn't have a feathery gill on its back like other nudibranchs.I also saw this little Yellow foot nudibranch (Thordisa villosa) that looks like a flatworm from above.Of course Chay Hoon, Marcus and James found even more splendid and colourful slugs and nudis. See links to their blog posts below.

There were also lots and lots of swimming crabs (Family Portunidae) of all sizes and shapes. As well as many mama Stone crabs (Myomenippe hardwicki) carrying eggs on their bellies.

Pulau Sekudu is full of small fishes! Many are well hidden among the seaweeds, or well camouflaged. Seagrass meadows such as Pulau Sekudu and Chek Jawa are a nursery for young fishes and other juvenile animals. Some of these eventually move into deeper waters when they grow bigger. And some are our favourite seafood.Clockwise from left: Filefish (Family Monacanthidae), halfbeak (Family Hemiramphidae), Copperband butterflyfish (Chelmon rostratus), an unknown fish, Chequered cardinalfish (Apogon margaritophorus), rabbitfish (Family Siganidae).

Alas, I came across a large fish trap that seems to be recently placed.The traps were wedged with rocks. Was it placed there at low tide? Tied to it was another trap further away. We had no time or manpower to deal with the traps on this trip. We should probably make a special trip just to clean up Pulau Sekudu of new and old fish traps and nets.

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